Researchers uncover role of repetitive DNA and protein sequences in tumor evolution

A team of researchers from the National Library of Medicine (NLM), part of the National Institutes of Health, and collaborating academic research institutions developed a method to measure a type of gene mutation involved in the evolution of cancer. This type of mutation, called “repeat instability,” may be useful in early cancer diagnosis.

Graph of somatic changes over time. Photo: Erez Persi, Ph.D.

Cancer is primarily caused by mutations in certain genes. The most thoroughly studied cancer-associated mutations involve the substitution of one nucleotide of DNA for another in genes known as oncogenes and tumor suppressors.

The researchers identified a different type of mutation active in cancer, one that increases and/or decreases repetitive segments of DNA and protein sequences in various genes. These changes are collectively named “repeat instability.”

Researchers developed a computational methodology to quantify variations in the repeat content of gene and protein sequences. They analyzed sequence data from 325 patients with a variety of cancers, including breast, prostate, bladder, and lung, as well as individual patients with metastases.

Using computational biology techniques, the researchers compared the sequences from the cancer tissue with those from healthy tissue adjacent to the cancer site and to blood, which served as the control.

“This study shows that repetitive sequences, which are ‘hotspots’ of DNA evolution, emerge early in tumor evolution but fade away in later phases, particularly during the transition to metastatic states, though they leave clear marks in the genome,” said Eugene Koonin, Ph.D., a co-author of the study and head of NLM’s Evolutionary Genomics Research Group.

“The study found that non-cancerous tissue adjacent to tumors had patterns of repetitive sequences that were similar to those detected in tumors,” said NLM’s Erez Persi, Ph.D., lead author on the paper. “This fact, and the reduction in repeat sequences seen once the cancers metastasized, suggests the potential for using repeat sequences in the early diagnosis of cancer.” (National Institutes of Health)

YOU MAY ALSO LIKE

Bright Spots Shine in Newest Dawn Ceres Images

New images of dwarf planet Ceres, taken by NASA's Dawn spacecraft, show the cratered surface of this mysterious world in sharper detail than ever before.

Fiery Collisions That Gave Birth to Earth Could Have Evaporated 40% of Our World

The ground under your feet was not always so firm. Earth is thought to have gradually coalesced in fiery collisions of smaller planetoids – and those hellish conditions can now explain an enduring scientific mystery.

Clay fights MRSA, other 'superbugs' in wounds

The use of mud or wet clay as a topical skin treatment, or poultice, is a common practice in many cultures. In fact, the concept of using mud as medicine goes back to the earliest times.

Genetics of the 2014 Ebola Outbreak

The Ebola virus can cause severe illness and death in people and other primates. The 2014 Ebola outbreak is the largest outbreak in history, with more than 3,600 infections and 1,800 deaths as of the end of August, according to the World Health Organization. The outbreak is the first in West Africa and the first to affect major cities.

Grafting helps pepper plants deal with drought

Joining a high-yield pepper plant sapling to the roots of a strong and resistant variety could help pepper farmers cope with lower rainfall, a study has found.

Ease of weight loss influenced by individual biology

For the first time in a lab, researchers found evidence supporting the commonly held belief that people with certain physiologies lose less weight than others when limiting calories.